Drill stem section



April 16, 1940. D. G. HAWTHORN DRILL STEM SECTION Filed Nov. 13, 1939 I lNV NTOR BYd Y ATTORNEYS.

Patented Apr. 16, 1940 UNITED STATES PATENT OFFICE DRILL STEM SECTION Application November 13, 1939, Serial No. 303,950

2 Claims.

This invention relates to drill stem sections. In one method of exploring sub-surface formations, the drill bit of a standard boring machine is used as an electrode for passing elec- ,tricity into the earth at the bottom of a bore hole in order to test the electrical response of the formation in which the bit is operating to determine the nature of such formation. The drill stem consists of a number of lengths of pipe joined together by standard male and female connectors provided at the ends of the pipe lengths. As shown in the patents to Hawthorn, Nos. 2,096,359 and 2,151,201, the pipe lengths have heretofore been provided with conduits to provide support and protection for a sectional insulated electrical conductor by which electrical current is supplied to the drill bit, each pipe length containing a conductor section having its ends connected to fixed contacts at the ends of the pipe length.

In a drill stem composed of such sections, the space between each conductor section and the inner surface of the enclosing conduit is open at both ends and during a drilling operation is filled with drilling fluid. Starting and stopping of the drilling fluid pump causes sudden application of pressure to the ends of the column of drilling fluid in the conduit causing inward movement of the drilling fluid from each end of the conduit. Due to the small area of the conduit in proportion to its length, such inward movement of the drilling fluid tends to cause the conductor to move toward the center of the conduit with consequent eventual breakage of the conductor. In order to protect the conductor from 35 contact with drilling fluid, asphaltic insulating compound has been introduced into the space between the conductor and the inner surface of the conduit. With such arrangement, the ends of the plastic compound are subjected to sudden applications of pressure resulting from starting. and stopping the drilling fluid pump, causing inward movement of the insulating compound and conductor as above described with consequent eventual breakage of the conductor, or damage to its insulation.

An object of this invention is to counteract the effect of sudden pressure applications to the ends of the conduit and thereby avoid injury to the conductor, or its insulation.

According to this invention, the conduit is provided with a plurality of longitudinally spaced apertures opening into the pipe by means of which the fluid pressure in the pipe is applied to the drilling fluid or insulating compound contained in the conduit at intervals throughout the length of the conduit. Such arrangement eliminates inward movement of the drilling fluid or insulating compound thereby avoiding the development of a breaking strain in the conductor. The perforations may be of any desired size and 5 shape and may be arranged as desired except that they must be distributed throughout the entire length of the conduit.

Other objects, novel features and advantages of this invention will become apparent from the following specification and accompanying drawing, wherein:

Fig. 1 is an elevation of one section of a drill stem connected at either end to another section;

Fig. 2 is a fragmentary longitudinal section of a drill stem section and coupler parts;

Fig. 3 is a transverse section of a section;

Fig. 4 is a section on the line 3-3 of Fig. 3; and

Fig. 5 is a view similar to Fig. 3 of a modification.

As shown in Fig. 1, the drill stem consists of a series of pipe lengths I0 joined by couplers or tool joints II. Each coupler consists of a male connector I2 and a female connector I3 which are permanently secured to the opposite ends of each pipe length and which are provided with co-operating tapered screw-threaded portions by the engagement of which the two connectors are joined to form a coupler II, such coupler construction being of the standard type now in general use and known as a tool joint.

A conduit I4 extends longitudinally of each pipe length I0 and is brazed or otherwise permanently connected to the inner periphery of the pipe. An insulated electrical conductor I5 extends through the conduit I4 with its ends projecting beyond the ends of the conduit as well as the ends of the pipe. Each of the connector members I2 and I3 is provided with a contact member I6 to each of which one end of the electrical conductor I5 is attached and which provide electrical connection between the conductors I5 in successive pipes or stem sections Ill. The connector I6 may be of the type shown in Hawthorn Patent 2,096,359 or of any other suitable construction.

As both ends of each conduit I4 are open to the interior of the stem, the conduit is filled with drilling fluid during the drilling operation. Provision is made for counter-acting the eiTects resulting from the sudden application of pressure to the ends of the conduit resulting from sudden changes in pressure in the drilling fluid incident to the starting and stopping of the drilling fluid pump. The desired counter-acting eflect is obtained by providing a plurality of apertures II in the conduit H, by means of which pressure existing in the drill stem is applied to the contents of the conduit at a plurality of points. These apertures may be of any suitable shape and size and may be located as desired, providing the arrangement is such that the apertures are distributed over the entire length of the conduit. By means of these apertures any sudden application of pressure to the fluid inside the drill stem is applied over the entire length of the fluid column in the conduit, thereby eliminating inward movement of the conductor at either end as would be the case if the apertures were not provided. By reason of the provision of the apertures, there is eliminated the possibility of breakage of the conductor due to inward movement thereof into the conduit by reason of pressure variations.

As illustrated in Fig. 5, asphaltic insulating compound l8 may be provided in the conduit between the conductor and the inner surface of the conduit for the purpose of removing that portion of the conduit in the conduit from contact with the drilling fluid. The arrangement of the apertures 21 is the same in this modification as above described, and they provide for application or the drilling fluid pressure to the insulating compound column over the entire length of the conduit, thereby eliminating inward movement of the conductor and compound at either end as would be the case if the apertures were not provided.

I claim:

1. A drill stem section comprising a pipe, a conduit attached to the inner wall of said pipe, an insulated electrical conductor in said conduit having its ends projecting beyond the conduit ends, said conduit being provided with longitudinally spaced apertures leading to the interior of said pipe whereby in a drill stem composed of a plurality of sections connected by couplers with the ends of each conduit open to the interior of the drill stem, the pressure of the drilling fluid within said pipe is applied to the interior of the conduit at longitudinal intervals to counteract the fluid pressure applied to the conduit ends.

2. A drill stem section comprising a pipe, a conduit attached to the inner wall of said pipe, an insulated electrical conductor in said conduit having its ends projecting beyond the conduit ends, and plastic material filling the space between the conductor and the inner surface of the conduit, said conduit being provided with longitudinally spaced apertures leading to the interior of said pipe whereby in a drill stern composed of a plurality of sections connected by couplers with the ends of each conduit open to the interior of the drill stem, the pressure of the drilling fluid within said pipe is applied to the filling material at longitudinal intervals to counteract the fluid pressure applied to the filling material at the conduit ends.

DAVID G. HAWTHORN. 

